Jet initiated drawing process



June 24, 1969 G. mm $452,130

JET INITIATED DRAWING rnocsss Filed Feb. 2, 1967 Sheet of 2 June 24,1969 G. PITZL 3,452,130

JET INITIATED DRAWING PROCESS Filed Feb. 2, 1967 Sheet 3 of 2 UnitedStates Patent U.S. Cl. 264-2 5 Claims ABSTRACT OF THE DISCLOSUREFilaments are orientation drawn by replacement of the usual snubbingdevice with a jet device through which the yarn advances toward a drawroll. In the jet device, drawing is initiated by exposure to anintersecting jet of a heated gaseous fluid such as air or superheatedsteam. Fluid temperature and pressure must be such as to heat the yarnto the drawn initiation point in less than ten milliseconds.

This is a continuation-in-part directed to subject matter divided frommy copending application Ser. No. 167,083, filed Jan. 18, 1962, now U.S.Patent No. 3,303,169. The invention relates generally to the productionof filamentary structures from synthetic linear polymers and moreparticularly to the processes by which such structures are drawn andoriented.

"It is well known that synthetic linear polyamide filaments are usuallydrawn to increased length in order to produce an oriented structurehaving high tensile strength. When nylon was first introduced, this stepwas accomplished merely by tensioning filamentary yarn between feed anddraw rolls operated at differential speeds. Although product quality wasacceptable, various difficulties such as differential dyeability wereencountered as a result of nonuniform tensile properties and variableorientation along the length of the drawn yarn. Subsequently, the use ofa snubbing pin in the drawn zone and localization of the drawn point onthe surface of the pin were disclosed by Babcock in U.S. Patent No.2,289,232. With this modification, yarn properties and uniformity areimproved substantially but additional process considerations such as theapplication of finish to the yarn for the purpose of reducing frictionare involved. To avoid variations in yarn properties, the amount,distribution and composition of the finish must be controlled carefully.For a given set of process conditions, there is an upper limit on thespeed with which yarn can be drawn in order to insure that adequate timeis available for the uniform application of finish to each filament of abundle. Similarly, where a heated pin is employed, there is a limitimposed on drawing speed by the minimum contact time required to heatthe running yarn sufficiently.

An additional problem which has been encountered in pin-drawing nylonyarn is that the drawn yarn undergoes a gradual lengthwise retractionwith time. These effects are accelerated by heat and moisture. Forexample, representative nylon yarns have a boil-off shrinkage of ormore. Where that degree of shrinkage is excessive, a separate shrinkingstep prior to utilization of the yarn is required. In addition to theextra processing and handling involved in such preshrinking procedures,the yarn usually suffers a reduction in initial modulus due to adiminution of yarn orientation and is therefore more sensitive totension variations encountered in subsequent processing stages.

The various improvements and advantages disclosed herein areaccomplished in a single-stage drawing process which includes the stepsof advancing a filamentary yarn 3,452,130 Patented June 24, 1969 iceover feed and draw rolls and substantially instantaneously heating thefilaments in the draw zone to a temperature of at least C. as they passthrough an enclosure. In the enclosure, a heated, single-phase gaseousfluid is jetted on the filaments in intersecting relationship therewith,thereby initiating drawing, reducing the drawing tension substantiallyand localizing a significant fraction of the draw in the enclosure.

As noted, the desired effects are attained when a yarn temperature of atleast 115 C. and preferably C. or more is reached. With a substantiallyinstantaneous increase in filament temperature to about C. much morestable operation and improved product uniformity are achieved. Themaximum operable filament temperature corresponds to the fiber sticktemperature which is generally about 2035 C. below the polymer meltingpoint. When this temperature is reached, it is believed that individualfilaments break and stick to the body of the jet enclosure, therebyfouling the yarn passages and rapidly breaking down the thread line.Broken filaments observed under these conditions show evidence offusing.

Where reference is made herein to a substantially instantaneous increasein filament temperature, the relationship between fluid conditions andyarn speed is such that the yarn is raised to the desired temperature inless than ten milliseconds, preferably in less than about onemillisecond. Under these circumstances, fluid temperatures above thepolyamide melting point are usually required but have no adverse effecton the yarn because of the high rate of speed at which it travelsthrough the fluid jet.

Although a substantially instantaneous increase in filament temperaturewithin the jet enclosure is essential to initiation of drawing, it isapparent that such temperature measurements oftentimes can only be madewith great difliculty. Furthermore, in the lower range of operablefilament temperatures, small variations can have a large effect on thedegree of fiber orientation and, for that reason, the close control ofprocess variables is important. In this respect, it has been found thatthe reduction in tension resulting from the transfer of heat to thefilamentary structures is an accurate reflection of the yarn temperaturein the jet enclosure. Since the reduction in tension can be measuredreadily, it is also useful as a control parameter and has been reportedherein as a process characterization. When the temperature and pressureconditions are sufficiently intense to raise the yarn to a temperatureof about 115 C., there is a corresponding reduction in tension in thedraw zone to about 75% of the tension observed when no heating fluid issupplied. Much greater improvements are obtained when the drawingtension is reduced to the 65% level and below.

In addition to yarn temperature in the jet and tension level in the drawzone, the extent to which the yarn is drawn is another process variableon which the degree of orientation is dependent. However, since as-spunyarn is partially oriented, reference to the draw ratio alone does notgive an accurate or reliable indication of the total orientationobserved in the drawn yarn. Where the phrase total draw ratio X is usedherein, the various types of orientation introduced into the yarn havebeen considered. Thus, the factor X includes the conventional machinedraw ratio X which is the ratio of feed and draw roll surface speeds ifno slippage occurs. Since the yarn entering the drawing stage may beunder slight tension, an added predrawing stretch ratio X may have beenimposed; usually this orientation factor is insignificant and can beignored. The as-spun yarn also has a degree of orientation, produced inthe spinning process and measured by filament birefringence, which canbe expressed as a draw ratio X With this information available, areasonably accurate indication of the degree of orientation can beobtained by computing the total draw ratio X which is the product of themachine draw ratio X and the as-spun orientation factor X In thefollowing specification and examples, reference is made to theaccompanying drawings wherein:

FIGURE 1 is a schematic illustration of an installation useful in thepractice of a split process;

FIG. 2 is an enlarged, longitudinal, sectional view of the singleorifice jet shown schematically in FIG. 1;

FIG. 3 is a schematic illustration of an installation useful in thepractice of a coupled process;

FIG. 4 is a longitudinal, sectional view of a two orifice jet suitablefor use as a replacement in the arrangements of FIGS. 1 and 3;

FIG. 5 is a perspective view, partially sectioned of another jetembodiment; and

FIG. 6 is a schematic illustration of an apparatus arrangement which hasbeen included for purposes of comparison.

In the process installation of FIG. 1 (Example I), undrawn nylonfilamentary yarn 10 is unwound from a package 12, moistened in itstravel over finish roll 14, passed between guide pins 16 and tensionedbetween driven feed roll 18 and draw roll 20. In order that thefilamentary structure will be drawn to several times its extrudedlength, rolls 18, 20 are operated at differential surface speeds, i.e.,roll 20 has a peripheral speed considerably higher than that of roll 18.From roll 20, the drawn filamentary structure passes between pins 22 toa suitable windup '24.

In the draw zone between rolls 18, 20, a jet device 26 of the type shownin FIG. 2. is positioned. Device 26 is provided with a longitudinalpassage or enclosure 27 through which the tensioned yarn travels.Intermediate its ends, passage 27 communicates with the orifice of a jetconduit 28, which is disposed at an angle of about 30 with the axis ofpassage 27. Device 26 is adapted for connection at 29 to a suitable highpressure fitting which functions to deliver a controlled supply of asingle-phase heated gaseous fluid to conduit 28 for discharge intopassage 27 in intersecting relationship with yarn passing therethroughin the direction indicated.

The process installation of FIG. 3 (Examples II, V) is similar to thatshown in FIG. 1 except that yarn 10 is spun from a spinneret 12' and atandem arrangement of two jet devices 26 is provided in the draw zonebetween rolls 18', 20'.

In other process installations (Examples III, IV and VII-IX), the jetdevices of FIGS. 4 and 5 are substituted for the device 26 of FIG. 1 orfor the devices 26' of FIG. 3. The device 40 of FIG. 4 is similar tothat shown in FIG. 2, except for the provision of two angularly disposedjet conduits 41, 42 discharging into the longitudinal passage 43 at anangle of 45. The jet device of FIG. 5 has an initial passage 51 throughwhich yarn travels to expansion chamber '52, passage 53 and tail pipe54. In chamber 52, heated fluid from four symmetrically disposed jetconduits 55 is jetted onto the yarn in intersecting relationshiptherewith.

The apparatus arrangement of FIG. 6 includes a plurality of pins 61which support yarn 62 in the draw zone as heated fluid is dischargedthereon from a plurality of jet conduits '63, each in communication witha manitold 64. This arrangement has been disclosed herein for purposesof comparison (Example V1) with operable embodiments wherein the yarn isin a passage or enclosure when exposed to the fluid jet. In thisrespect, it should be noted that the embodiments of FIGS. 4 and 5 have apassage or enclosure equivalent to that shown at 27 in FIG. 2, i.e., apassage which is completely enclosed except for the yarn inlet andoutlet. and the jet orifice(s) Other constructions are feasible. Forexample, a device comprised of a pair of opopsed flat plates betweenwhich the yarn travels as fluid is jetted thereon from an orifice in oneof the plates is operable under certain conditions. The principalrequirement is that the heated fluid must impinge on the yarn in an atleast partially restricted zone. Fluid expansion in that zone of contactor impingement contributes to a separation of the yarn bundle and to thesubstantially instantaneous increase in filament temperature which isessential to the instant process. When these conditions are achieved,heat transfer from the gas to the yarn is optimum, due at least in partto separation of the filaments in the yarn bundle during such treatment(Example III). The separation of the filaments also helps to avoidfusing at high gas temperatures.

Any gas reasonably inert to the yarn may he employed as the jet medium,hot air or superheated steam being preferred in most applications. Otherpossibilities include nitrogen, carbon dioxide and mixtures thereof.Saturated steam is believed to adversely affect the yarn modulus attemperatures required to obtain minimum yarn shrinkage. In addition, thepresence of condensate on the drawn yarn is though to contribute toproduct nonuniformity.

The temperature and pressure of the heated, single phase gaseous fluidmust be carefully controlled to maintain a product with uniformproperties. At constant pres sure, the temperature of the fluiddetermines the amount of tension in the yarn during drawing as well asthe shrinkage and retraction of the product. Any increase in fluidtemperature at constant pressure results in a substantial decrease inall three values, the upper limit usually being set by temperatures atwhich filaments fuse or break in a given jet. Conversely, at constanttemperature, an increase in fluid pressure not only results in adecrease in the yarn tension during drawing but also leads to a furtherreduction in the residual shrinkage and retraction of the drawn yarn.The temperature and pressure selected will also depend on yarn speedbecause of its relationship to the period of yarn exposure to the jetmedium. A comparison (Table I, runs AF and AK) of the relativeefficiency of superheated steam and hot air at the same pressure, usingthe same fluid jet, shows a distinct temperature advantage in favor ofsteam, as reflected by the level of tension during drawing and by theshrinkage and retraction of the product.

In the examples which follow, the use of different combinations of theillustrated apparatus under various drawing conditions has beendescribed. When polyamide filaments are drawn in accordance with theminimum process requirements, the drawn yarn is characterized by highmodulus and tenacity as well as by low shrinkage and retraction. It alsohas good mechanical quality and excellent property uniformity. Sincesnubbing elements are not employed, the problems previously encounteredwith friction and finish uniformity are avoided.

Under the more severe process conditions reported in some of theexamples, an unusual and hitherto unobtainable combination of propertiesis achieved in that the drawn yarn has a break elongation of at least25%, an initial modulus of at least 38 grams/ denier and a boiloffshrinkage of not over 6.5%. X-ray analysis shows that the crystallinestructure is highly oriented and has a large transverse area. Theaverage X-ray orientation angle is preferably less than about 14, andthe crystal cross sectional area is at least 1250 square angstroms,preferably at least 1500 A measured prior to boil-off, relaxation oranneal-ing treatments. This product is so stable that, even afterboil-ofi, its high modulus is largely retained, and fabrics woventherefrom are characterized by an unusually high crease recovery,indicating superior wrinkle resistance and resilience.

The yarn samples employed in the exemplified tests and comparisons wereobtained by stripping representative -150 cm. lengths from theextremities and from the longitudinal center of a package, throughoutthe entire package and yarn length.

Where retraction is reported, sample length was determined immediatelyafter removal from the package by tying the ends of the sample together,hanging a weight equivalent to about 0.1 g.p.d. in the loop andmeasurlng loop length. After exposure for 24 hours at 75 F.

described by C. W. Bunn and E. V. Garner, Proc. Royal Soc., 1898A, 39(1947), for example. Crystal orientation is actually calculated from thehalf widths of the equatorial reflections, determined from an azimuthalphotometer trace, following the methods described by H. G. In-

(24 C.), 72% relative humidity, loop length Was m 5 gersol in Journ.Appl. Phys, 17, 924 (1946). Crystal diured again and percent retractionwas calculated. mensions are estimated from the breadth of thesedltfrac- For shrinkage values, yarn samples were taken from tion spots,measured from equatorial photometer traces, p g which had beenconditioned for one y at according to the method of H. P. Klug and L. F.Alex- F. (24 C.), 72% relative humidity. After determination l0 ander,X-Ray Diffraction Procedures, John Wiley and of the initial length, -aloop of conditioned yarn was sub- Sons, Inc., New York, 1954, Ch. 9.Warrens correction merged i b ni t r for about 20 minutes and then forline broadening due to instrumental effects was used as dried for about25 minutes under 0.1 g.p.d. tension. After a correction for Scherrersline broadening equation. Zinc measuring the length of the rboiled-oifloop, percent oxide was the reference material. A value of 0.9 wasemshrinkage was calculated. ployed for the shape factor K is Scherrersequation.

The initial modu s, rep e n e y the Symbol 1 Where reference is made tothe relative viscoslty of is defined as the ratio of change in stress tostrain in the polymer o ya it w d t rmin d as d ib d i US, firstreasonably linear portion of a stress-strain curve. The Patent No.2,385,890. units employed herein make the initial modulus numer- ExampleI ically equ1valent to 100 times the force In grams per denier requiredto stretch the specimen the first 1%. In the ex- A 34 filament yarn wasspun from molteri polyhexaamples, the modulus is obtained from yarnstress-strain methylene adipamide havmga relativevlscosity of aboutcurves recorded on an Instron Tensile Tester of the type 33.5 andcontarnln'g 0. t tanl m d oXlde as de which stretches the yarn at aconstant rate of elongation. trant, packaged and subsequently drawn 4.0X1n the From the stress-strain curve, the slope of the initial straightapparatus of FIGS. 1 and 2 to a nominal as-drawn den er line portion isdetermined graphically. Tenacity and break of 70 at a speed of 1000yards/minute (915 meters/mmelongation are also read from the curve. Allyarn tested ute). The undrawn yarn had a ablrefrlngence of 0.005 corwasconditioned on the package for one day at 75 F., responding to a spmnmgdrawn ratlo X of 1.12. The total 72% relative humidity, prior totesting. draw ratio X was therefore 4.48. After drawlng, the yarn It isbelieved that the maximum benefits of the proc Wohnh at tension of Pgrams on of this invention are attained when the yarn is heated indrlVeIl reclpfocatlng traverse f p- The results Obtamed the jetenclosure to a sufficiently high temperature to under various conditionsof fluid temperature and pressure achieve a pseudo-hexagonal crystalstructure, as deterare reported (runs AC-AO) in Table I. In each of runsmined by X-ray diffraction. The yarn is observed immethe heated fiuldWas at a pressure of pa -gdiately after leaving the jet enclosure.Temperatures ap- 35 (4.4 atm.). In runs AN and A0, the pressures were 25proximating the force-to-draw transition are usually and p.s.1.g. (2.7and 5.4 'atmQ, respect1vely, required to produce this structure, Runs AAand AB have been lncluded for purposes Of The force-to-draw transitiontemperature is the tem- Ih ah hhheated Shhhhlhg plh of the type peratureat which a discontinuity is observed in the ratio (hsclosed by Babcockwas p oyed. In AB, the yarn was of the logarithm of the tension requiredto draw an 40 uncontrolled 1n the draw zone, 1.e., ne1ther a pm nor adrawn filament versus the reciprocal of the drawing temfluld Jet wasemployed perature, as expressed in degrees on an absolute temper- Areferehc? to the drawlhg tehslohs and yam Proper ature scale. Theforce-to-draw transition temperature is hes reported In Tahle I Showsthat the h h fh conveniently determined by forwarding filamentary yarnpresent process begin to h f when fiuld Jet Commons from the SpinningWindmp packaue at 21/2 yards per 45 are such that drawlng tension 1sless than about of O D 9 I a me (23 meters per minute), to and about ahot steel that measured for the delocallzed control 1n run AB, 1.e.,when the yarn temperature 1n the et enclosure exceeds snubbmg pm one1nch (2.5 cm.) in dlameter and prov1ded h 1 t d u fi h th b d C. In thlsrespect, much better yarn properties are m a c rome'p 6 ma f ms e yarn ffawn obtained with tensions less than about 65% of AB (filam; Thehrawlhgforce 15 measured the h temper 50 ment temperatures above 119 C.). Undercorresponding athhe 1S vaned; From a f' of the se h h h the Q conditionsof temperature and jet pressure, superheated ordinates prev1ouslyspecified, the d1scont1nu1ty is readily Steam (AK) is a more effectiveheat transfer fluid than 1dent1fied and evaluated. hot air (AE).Equivalent yarn properties are obtained at Crystal onefltatlon andaverage lateral Crystal l a given tension level, regardless of theidentity of the jet sions of the h1gh modulus product of this inventionare 55 gas. determined from the principal equatorial X-ray diffractionIn addition to initiation of drawing, the tabulation maxrma. Polyamldedlifraction patterns of this type are shows that more than 25% of thedraw must occur (AF TABLE I Heat transfer- Draw zone Yarn propertiesTension, Percent Fluid temp., Yarn Tension, percent draw in en-Shrinkage, Retraction, Initial mod- C. temp., C g.p.d. control closurepercent percent ulus, g.p.d. Draw pin 2.38 98. 0 9, 8 2. 2 31. 6Delocalized 2.43 100.0 9. 9 2. 3 31. 8

control and A] in the yarn passage of the jet device in order to achievethe desired combination of properties. Preferably (AG and AK), at least50% of the draw is localized in that passage. By comparison with theaccepted view that 100% of the draw should be localized at a snubbingpin 8 Example III Under the conditions shown in Table III, additionalruns are made, using the same prepackaged yarn as in Example I and thetandem jet arrangement of Example i or its equivalent 1n order to obtaincontrolled drawing, J2 iomparabl? ig g ig g zgz ig it is interesting tonote that good yarn properties are obg gfi g A additional Su tained atmuch lower percentages of localization in the a e P Pmsent rocess portfor the conclusion that an equivalent combmation p Exam 1e H ofproperties can be achieved at a somewhat higher tenp 10 sion level withprepackaged as against freshly spun yarn. In an apparatus arrangement ofthe type shown in A similar comparison with runs AI-AL (Table I) shows3, 34 filament y was p from molten P Y- that more effective heating isaccomplished with the tanhexamethylene adiparnide of 33.5 relativeviscosity and dem jet arrangement .and that incremental property imdrawncontinuously to a total draw ratio of 4.5X. The l provements areobtained as the treatment conditions beyarn was drawn to a final denierof and wound at a 5 come more severe. speed of 2000 yards/ min. (1830meters/min), at a ten- The test is then repeated using the jetembodiment of sion of 7-10 grams. The two jet devices were spaced FIG. 5in which superheated steam is jetted onto the yarn apart 1.5 inches (3.7cm.) along the yarn line. With this from four orifices disposed inplanes at right angles. Yarn tandem arrangement, effective heating ofthe yarn at the properties and test conditions for runs CE-CI are alsohigher winding speed was achieved. Results obtained in reported in TableIII. The results show that, with no a series of tests using superheatedsteam at diiterent temincrease in steam temperature, drawing conditionsand peratures and pressures are reported in Table II. yarn propertiesimprove with each increase in steam pres- The percent crystallinity wasdetermined by the density sure. On the basis of these improvements, itis believed method of Starkweather and Moynihan, Journal of Polythat animportant factor in obtaining the advantages of rner Science, 22, 363(1956). The determinations are a the process of this invention is toprovide gas to the jet based on an estimated density of 1.069 foramorphous conduit at a sufficient pressure so that the yarn bundle nylonand a density of 1.220 for the crystalline regions. will be separated orsplayed by vibration or otherwise into The density of yarn samples wasdetermined by the methits individual filaments as a result of theimpingement of TABLE 11 Heat transfer Draw zone Yarn properties Steampressure Steam temp, C. Yarn Tension, Shrink- Retrac- InitialCrystalternp., Tension, percent, ag tion, modulus, linity, P.s.i.g.(Atm.) Jet #1 Jets #2 C. g.p.d. control percent percent g.p.d percentNone 1. 81 100. 0 3. 0

50 4. 4) 250 260 86 1. 79 99. 0 50 4. 4) 270 290 1. 64 90. 5 70 (5. s)250 250 114 1. 50 82. 9 50 (4. 4 280 280 114 1. 43 79. 0 5o (4. 4) 295295 115 1. 3e 75. 2 50 (4. 4) 290 310 116 1. 29 71. 3 70 5. s) 280 280117 1. 21 es. s 10 (5.8) 265 285 120 1. 14 e3. 0 70 (5. s) 270 290 1. 0759. 1 7o (5. s) 280 290 125 1. 07 59. 1

0d of Boyer, Spencer and Wiley, J. Poly. Sci., 1, 249 the jet or jetsthereon. As evidence to support this (1946). hypothesis, drawn 70 denier34 filament yarn was at- From a review of the data in Table II, it isapparent tached to a fixed support, passed through the jet of FIG. thatthe desirable combination of properties is not 5 and thence over apulley. A weight was attached to the achieved, with freshly spun filaments, until drawing tenyarn. The jet for this experiment was equippedwith a sions are reduced to a somewhat lower level than was re- 50 glasstail pipe so that the yarn could be more easily o'bquired with theprepackaged yarn of Example I. It is served. Room temperature air waspassed through the also apparent that the yarn properties improve as thejet. At an air pressure of 50 p.s.i.g. (4.4 atm.) and at a treatmentbecomes more severe. Although good results dead load corresponding tothe yarn tension in run CF, are achieved when tension is reduced to from65-70% W the yarn was observed to vibrate. It was observed that of thecontrol run BA, a greater incremental improvethe air pressure mustexceed 25 p.s.i.g. (2.7 atm.) in ment is observed when the drawingtension is less than order to maintain stable vibration. It wasconcluded that 60% of control. It is observed that the increasedstability the air pressure in runs CF-CI is in the range required of theyarn (to retraction and shrinkage) is obtained with to initiate andmaintain stable vibration or splaying of some increase in modulus, whichis contrary to expecta- 60 the yarn bundle, at the drawing tensionobserved. tions.

TABLE III Heat transfer Draw zone Yarn properties Steam pressure Steamtemp, C. Yarn Tension, Shrink- Retrac- Initial temp. Tension, percentage, tion, modulus, Tenacity, Run 1 P.s.i.g. (atm.) Jet #1 Jet #2 g.p.d.control percent percent gpd. g.p.d

i jets: 2. 43 100. o s. s 2. 3 31. s 1.22 52.3 4.8 1.2 32.6 1. 22 52.34.8 1.2 34.8 1.14 48.8 3.5 0.8 3&1

Elongation, percent.

After replacing the illustrated jet device with that shown in FIG. 4,the apparatus arrangement of FIG. 1 was used to draw prepackaged 34filament 6-6 nylon 10 Example VI Prepacka-ged 34 filament 6-6 nylon yarnhaving a birefringence of 0.005 and a relative viscosity of 38.5 wasdrawn to a machine draw ratio X of 4.0 in an apparatus yarn(birefringence 0.005) of 36.5 relative viscosity at arrangement of thetype shown in FIG. 1. The results a machine draw ratio X of 4.0. Theyarn was drawn obtained under various jet conditions and with differentto a final denier of about 70 and wound at a speed of jet devices havebeen reported in the 'following table in 500 yards/min. (450meters/min). For purposes of comorder to illustrate the advantage ofhaving the heated fluid parison, delocalized control run EA and pindrawn run impinge on the yarn in an at least partially restricted EBhave been included in Table IV. zone. IA is a delocalized control run.In J B, an enclosed The increased crystallinity of the test yarns (runstwo-orifice jet device of the type shown in FIG. 4 was EC-EG) comparedwith the pin-drawn control yarn used in place of that shown in FIG. 1.For runs JC-JF, (run EB) is readily apparent. The surprising tensilepropthe jet device Was replaced with the arrangement of FIG. erties ofthe yarns of this invention are also demonstrated. 6. For run JG,conduits 63 were located opposite pins 61 For example, in the series ofruns EC to EG, the yarn rather than between them. In JC-IG, temperatureswere tenacity is seen to increase appreciably while the yarn measured atthe orifice of a jet conduit 63. The yarn was elongation (breakelongation) remains substantially drawn and wound at a speed of 500yards/minute (450 constant. meters/ min.

TABLE IV Heat transfer Draw zone Yarn properties Steam pressure SteamYarn Tension, Elonga- Crystaltemp., temp, Tension, percent Tenacity,tion, linity, P.s.i.g. (Atm.) 0 C. g.p.d. control g.p.d. percent percentNone 2. 86 100. 0 35. 5 None, draw pin 2. 50 87. 5 5.1 27. 5 34. 1 50(4. 4) 260 116 2. 07 72. 4 5. s 27. 2 35. 1 50 (4. 4) 270 119 1. 86 65.05. 9 27. 0 35. 5 50 (4. 4) 295 121 1. 79 62. 6 6. 0 27. 2 36. s 60 (5.1)260 123 1. 72 60. 2 6. 1 27. 7 36. 3 60 (5. 1) 290 126 1. 65 57. 7 6. 328.2 36. 1

Because of the numerous filament breaks at the sup- Example V portingpins, runs IF and JG were deemed lnoperable. nd t COIldltlOIlS forthfreshly In JE, drawing tension was reduced to 68% of control ep nylon Yof e Y VlSeOsltY drawn JA. However, yarn shrinkage and retractionpercentages In an apparatus g h h slmllaf t0 were considerably in excessof those obtained in test run 3 eXCePt for the Othlssloh of one Of the Jdevlees JB, i.e., with the enclosed jet device of FIG. 4. In run I D,and e t e Q the Y P e enclosure III the drawing tension was reduced to71.5% of control IA, Iemahllhg J devlee- The heated fiuld Wassuperheated but shrinkage remained at the relatively high level of steamand the windup speed was 2000 yards/min. (1830 40 9 a l I. nie iformitof meters/mm) as in Ex mpe I De r un y Example VII TABLE V Thirty-fourfilament, 33.5 relatlve v1scos1ty poly(hexa- Heat transfer Draw zoneProduct methylene adipamide) yarn of 0.005 birefringence was st st Tdelflier spun at 500 y.p.m. (450 meters/min.) and packaged. e121,? 3%Tension, 535 23,} 2,3 The packaged yarn was drawn in the apparatusarrange- Run 0. si-g- (A an control ment of FIG. 1, using thetwo-orifice jet of FIG. 4, at a FAN" None, pimdmwn control 21 draw ratioX of 4.0. The yarn was drawn to a denier of control 28-? H about 70under the conditions and at the speeds indicated in Table VII. KA is adelocalized (no pin, no jet, room Percent coefficient of variation.temperature) t l runthis yarn and of two control yarns, as reported inthe X-ray examination of the drawn yarn according to the above table,was determined automatically by capaprocedures described previouslyshows that they have TABLE VI Heat transfer Draw zone Yarn propertiesSteam pressure Steam Steam Yarn Tension, Shrink- Retractemp., flow, tempTension, percent age, tion Run P.s.i.g. (Atm.) C. c f.m. g.p. controlpercent percent;

N one-control 3. 15 100. O 10. 5 2. 5 35 (3. 4) 1. 22 38.7 4. 0. 9 70(5.8) 3. 15 100. 0 10. 6 2. 4 70 (5. s) 2. 25 71. 5 9. o 2. 1 70 (5.8)2.15 68.3 8.3 1. 9 70 5. s) 2.07 65. 7 7. 5 1. 7 70 (5.8) 2. 07 65. 7 7.6 1. 8

itance variation measurements using a Model C Uster Tester.

Drawing tension for run PC is within the scope of the invention. Thedata in Table V show that the test yarn (run PC) is more uniform thanthe pin-drawn control (run FA) or the cold-drawn control (run FB). As inthe preceding examples, the mechanical uniformity of the product and theoperability level of the process are generally superior to those of thecomparable operations involving a draw pin or other snubbing element.

exceptionally large transverse crystal cross sections, combined with ahigh degree of orientation, as indicated by the low orientation angles.The results are given in Table VIII along with corresponding values forshrinkage and modulus. Also included, for purposes of comparison, is apin-drawn control KF prepared from similar yarn spun at 1500 y.p.m.(1370 meters/min), packaged, then drawn 2.90X at a tension of 2.5 g.p.d.KF has a spun yarn birefringence of 0.020, corresponding to a drawnratio X of 1.56. The total draw ratio is, therefore, 4.5X.

The novel product obtained under the process conditions of run KD has aconditioned modulus (on the drawing package) of at least 38 and. and aboil-off shrinkage of not over 6.5%. This product is characterized by acrystallite cross section of at least 1250 A? and an From the tabulatedresults, it is apparent that jet drawn yarn (LA) has a higher initialmodulus than conventionally drawn yarn (LB) and also retains a somewhatgreater fraction of the initial modulus after boil-01f. The latterimprovement correlates well with the improved crease orientation angleof less than 145. Even more desirable recovery of the scoured fabric.products, characterized by a crystallite cross section of Exam 16 IX atleast 1500 A? and an orientation angle of less than p 14.0", areobtained under the process conditions of Ten f i polflhexamethylfineadlPamlde) y f run KB 35.5 relative vlscosity was spun and drawn at themaxib1 d Exam 1e VH1 mum opera e machine raw rat1o and to a denier of 60p 1n an apparatus arrangement of the type shown in FIG. Prepackaged 34filament 6-6 nylon yarn having abire- 3, using the jet device of FIG. 4.As a treating fluid, fringence of 0.005 was drawn (LA) in a FIG. 1apparatus steam was delivered to the jet at a pressure of 30 p.s.i.g.arrangement, using the jet device of FIG. 4. Draw con- (3.0 atm.) and atemperaure of 315 C. The drawn yarn ditions were as follows: steampressure p.s.i.g. (3.0 was wound at a speed of 2000 yards/min. (1830meters/ atm.), steam temperature 275" C., machine draw ratio min).Various drawing conditions and yarn properties X 4.0, windup speed 500y.p.m. (450 meters/min). A for test run MA are reported in the followingtable for control (LB) was prepared from the same prepackaged purposesof comparison with the corresponding values yarn under the same drawconditions except that an un- 29 obtained in run MB in which the jetdevice was replaced heated pin was used. In both runs, modulus with anunheated draw pin.

TABLE V11 Windnp speed Heat transfer Draw zone Steam pressure SteamSteam flow Yarn Tension, Tension, Y.p.m. (Meters/min.) temp., mp.,g.p.d. percent p.s.i.g. (Atm.) C. C.t.m (Liters/min.) C. control 1, 000(910) Delocalized Control None 2. 64 100. 0 1,000 (910) 30 (3. 0) 280 2.9 (52) 116 2. 0o 75. 7 1, 000 (910) (3. 7 285 3. 6 (102) 117 1. 79 67. s750 (640) 40 (3. 7) 285 3. 6 (102) 124 1. 57 59. 4 500 (450) 40 (3. 7)285 3.6 (102) 139 1. 3e 51. 5

TABLE VIII Yarn properties Crystallite dimensions Shrinkage, Tenacity,Elongation, Width, Breadth, Orientation angle Mi, g.p.d. percent g.p.d.percent A., D A., D Area, A?

IA IO Average 34. 1 10.7 5. 0 27. 3 34 23 780 15. 7 14. 7 15. 2 37. 5 9.5 5. 4 2s. 2 as 25 900 14. 2 14. 0 14. 1 37. 6 7. 8 5. 5 25. 2 39 25 97514. 2 13. 6 13. 0 3s. 2 6. 5 5. 4 25. 2 43 29 250 12.4 12. 4 12. 4 3s. 25. 5 5.0 30. 3 52 33 1, 720 12. 3 12. 0 12. 2 33. 5 10. 0 37 23 850 15.0 15. 0 15. 5

was determined on as drawn yarn samples and also TABLE X after boil-ofi.Thereafter, fabric samples were prepared R from the yarns of runs LA andLB by weaving 104 x 75 MA MB count taffeta and scoured in theconventional manner. grawrati mxm 5.60 4. so The crease recovery isdetermined by means of a modified 532352? ;}g 5: 572 Monsanto creaserecovery test which provides an accurate fi pg c nt-n 18.? 20. 3measurement of fabric resilience. All result are reported j g i l fggggi t 33: "15 rys a mi y, ercen .3 33.0 m Table 1X Coeificieni; of denier variation, percent 1. 4 2. 0

T E 1X ABL From Table X, it is apparent that the process of the Run LALB invention (run MA) permits drawing at higher draw As drawn, M1 40.427.8 ratios to obtain yarn of higher tenacity, modulus, crystal- Afterboibofi, i -P' linity and denier uniformity, at constant drawingtension, Percent crease recovery war 55.1 43.3 as compared toconventional pm drawing (run MB). Fllllng..- When the test was repeated,using yarn spun from Average 7Z3 high viscosity vacuum-finishedpoly(caproam1de), similar result were obtained. The generally acceptedmethod for measuring crease Example X recovery is the Monsanto testwhich has been described as the Vertical Strip Crease Recovery Test inthe A polymer mixture consisting of 80 parts polyhexa- American Societyfor Testing Materials Manual. For methylen? ad}Pam1d@ and 20 Partspolyhexamethyleneiso' the purposes of this example, the test wasmodified by Phthalamldfi 1S p to a 14 fi1ament y at Yards P placing aplate 0.070 inch (1.8 mm.) thick within the mlf'llfie meiers P m1nute)and lmmedlately drawn fold of the fabric being creased, thus producing amuch (wlthoutpackagmgi at the maximum p a ma less sharp crease in thefabric than obtained by the standdraw Iat10- test P p a l slmllflf t0ard method. Recovery from this crease (in two minutes) that shown inFIG. 2 15 used in the draw zone. This jet,

was determined according to the specified test procedure.

however, has a constricted yarn inlet, slightly larger than the yarnbundle. The outlet, for yarn and steam, is rectangular in cross section.There is a narrow slot parallel with and connected to the yarn passage,permitting easy stringup. The jet is fed with 250 C. superheated steamat 50 p.s.i.g. For comparison, a control NB is also run at maximumoperable draw ratio, using identical yarn and an unheated snubbing pinin the draw zone. Yarn properties are given in the following table.

Example XI A composite filament yarn is prepared substantially asdescribed in British Patent 950,429. The filaments consist of a sheathof 6-6 nylon (polyhexamethylene adipamide) of 40 relative viscosity andan eccentrically disposed core of a random copolymer which is 50 weightpercent 6-6 and 50 percent 6-10 nylon (polyhexamethylene sebacamide) of48 relative viscosity. Technical grade sebacic acid is used.Substantially equal amounts of each component are used in each compositefilament. The polymers are melted and extruded to a 7 filament yarnusing a spinneret arrangement substantially as in FIG. 2 of the Britishpatent. The spinning speed is 1000 yd./min. (915 meters/ min.). Thebirefringence of the component of spun yarn having the higherbirefringence is 0.016. After quenching by a transversely directedcurrent of air, the filaments are forwarded to the draw zone by means ofa feed roll and associated separator roll and pass in multiple wrapsaround a pair of driven draw rolls, thence to a tension letdown rollfollowed by a reciprocating traverse, surface driven windup. The finalyarn denier is about 41. Spinning speed is kept constant at 1000yd./min. (915 meters/ min.), and the draw ratio is varied by changingthe speed of the draw rolls. For most of the tests, a jet similar toFIG. 2 is placed in the draw zone. The yarn passage 27 is rectangular incross section, inch wide by 4 inch deep (2.4 mm. x 6.3 mm.), and it isabout 5 inches (12.7 cm.) long. Air inlet 28 is 0.08 inch (2.0 mm.) indiameter. An inverted U-shaped warn guide is placed in the yarn passage27, just before the point where hot air contacts the yarn. The airpressure is 80 p.s.i.g. (6.45 atmospheres). Yarn temperatures in the jetenclosure are estimated from low draw, yarn uniformity is poor. When hotair is introduced into the jet, the draw initiation point moves into thejet enclosure, even at higher draw ratios. In Run 4, it is noted that anair temperature of 150 C. is insuflicient to raise the filaments to therequired temperature. Under these conditions, the draw initiation pointmoves out of the jet enclosure and numerous yarn defects (brokenfilaments) are observed. It is further observed that increasing airtemperatures permit the use of higher drawn ratios to provide increasedyarn tenacity, along with improved uniformity of sonic modulus andinterfilament denier, and also fewer defects such as broken filaments.

Example XII In order to develop the maximum crimp potential in thecomposite filament yarn of Example XI, the drawn yarn is subjected to aprecrimping heat treatment. In this case, the precrimping step iscarried out by passing the yarn through another jet supplied with heatedair at 90 p.s.i.g. (7.1 atm. absolute), after it leaves the draw rolls.The precrimping jet is like the draw jet, except that the yarn pathchannel is expanded in a funnel-like cross section to give an exit airvelocity of about 60 ft. (20 meters) per minute. The unheated tensionlet-down rolls are operated at a lower surface speed than the drawrolls, to permit the drawn yarn to retract (relax) and crimp in the jet.It is then cooled and stretched enough to remove the crimp prior towindup. The development of final crimp occurs after this yarn isconverted to fabric (e.g., knitted or woven), as it is boiled off. Thecrimp retraction of the yarn against restraint is a measure of the crimpobtainable when the fabric is boiled off, and is measured as describedon page 5, lines 1646 of British 950,429. In preparation for thesetests, the effect of different draw ratios was studied. The airtemperature in the draw jet was increased until the draw initiationpoint was observed to enter and remain within the jet enclosure. It wasobserved that this occurred at a drawing tension of 35 to 40 grams,independent of draw ratio. A draw ratio of 3.7 and an air supplytemperature of 210 C., 80 p.s.i.g., were selected as giving goodtenacity, yarn uniformity and operability.

Under the above drawing conditions, air temperatures in the precrimpingjet are varied in order to obtain the greatest crimp retraction. Theextent of yarn relaxation between draw rolls and windup is 16%. Theresults are listed in Table XIII.

measurements of yarn temperatures outside the jet en- TABLE XIIIclosure.

Precrimplng Crimp Properties of the yarns produced under varlous operat-Run jet air retraction, ing conditions are reported in Table XII, alongwith umtemp-Y Percent formity of sonic modulus, denier uniformity andyarn 1 220 27.1 2 230 27.1 qua a 240 26.7 It is observed that when theet 1s not used (Run 1), a 4 250 23.8 draw of 3.04 is the maximum thatcan be used; when this TABLE XII Yarn quality Draw jet; Yarn propertiesDefects Percent Percent Machine Air Yarn E1ong., sonic mod. denier PeRun No draw ratio temp., C. temp., 0. Ten., g.p.d. percent variationuniformity 10 yd 10 meters 3. 04 Unheated Unheatecl 3. s 54 20. 0 2.5 1. 1 1. 2 3.1 275 143 3.6 42 9.0 1.4 0.13 0.14 3. 3 300 148 3. 8 32 9.0 1. 9 2. 1 3. 5 150 81 4. 7 38 15. 7 42. 3 44. a 3. 5 300 144 4. 4 298.8 1. 5 0. 20 0. 22

ratio is exceeded, the draw initiation point moves to the Best resultsare observed when the precrimping jet is feed roll and broken filamentsare produced. Even at this operated at 10 to 30 C. above the draw jet.

When superheated steam is used in the draw jet in place of heated air,similar results are obtained, but at somewhat lower steam temperatures,due to its greater efliciency as a heat transfer fluid.

The process of thi invention is useful in the drawing of most syntheticlinear polycarbonamides or nylons, such as those disclosed in US.Patents Nos. 2,071,250 and 2,071,253. The preparation and spinning ofthese compounds is described in US. Patents Nos. 2,130,948, 2,163,- 636and 2,477,156. Particular example of such polyamides are those preparedfrom suitable diamines and dibasic acids, e.g., from hexamethylenediamine and adipic acid and their amide-forming derivatives, and alsofrom terminalamino carboxylic acids, e.g., from omega amino caproicacid, omega amino undecanoic acid and their amide-forming derivatives,such as caprolactam. Yarns spun from copolyamides, grafted polyamides,blends of polyamides with other compatible polymers and differentiallyshrinkable polyamide component may also be drawn to good advantage inthe process of this invention.

The process is particularly useful in drawing polyamide yarns at highspeeds, requiring substantially instantaneous yarn heating. Althoughmarked improvements are obtained at 500 y.p.rn., the higher velocityjets disclosed herein, which effectively heat the filaments to therequired temperature at exposure times (in the jet enclosure) in theorder of from 0.01 to 0.001 second, permit drawing speeds of 2,000y.p.m. or more, a level unattainable by prior art processes.

As disclosed in detail in my copending application Ser. No. 591,850,filed Nov. 3, 1966, the process is also useful in the drawing offilamentary yarns spun from polyesters. Particular examples arepolyethylene terephthalate and the copolyester prepared from ethyleneglycol and a 98/2 mixture of the dimethyl esters ofterephthalic/S-(sodium sulfo)-isophthalic acid. Other examples ofcrystallizable, linear condensation polyesters are polyethyleneterephthalate/isophthalate (85/ 15), poly-p-hexahydroxyleneterephthalate, polydiphenylolopropane isophthalate,polydiphenylolpropane carbonate, the polyethylene naphthalenedicarboxylates and poly-m-phenylene isophthalate.

The instant process permits very effective single stage drawing, and maybe followed by such important operations as setting, relaxing, twisting,crimping, alternate twisting, false twisting, and the like. The instantprocess is also useful in drawing filaments of modified cross section,e.g., Y, propellor-shaped, triolbal, etc., since substantially nodistortion of the desired cross. section is involved.

Advantages of the instant invention over prior art procedures includereduced drawing tensions, leading to improved process operability andproduct mechanical 11111- formity; elmination of snubbing elements,thereby avoiding frictional problems and the necessity for uniformfinish application; and the provision of yarn having reduced shrinkageand retraction values, such yarn being provided in a single step andcharacterized by both a high retention of initial modulus and improvedcrystallinity. The drawn yarn can be packaged at reduced tension, owingto its dimensional stability. Furthermore, this yarn can be preparedover a. wide range of tenacities at a given elongation. The process canbe carried out in a rapid, continuous and economic fashion using eitherfreshly-spun or packaged yarn.

Use of freshly-formed or as-spun yarn, prior to initial packaging, inthe practice of thi invention is particularly advantageous. Since theas-spun yarn is relatively amorphous, maximum reductions in drawingtension plus added flexibility in drawing and associated operations arefacilitated. The necessity of a separate drawing stage or step iseliminated, thereby leading to better mechanical quality due to reducedhandling, uniformity of lag time (between spinning and drawing) andelimination of an intervening packaging step. Over-all process economyresults. However, freshly-formed yarn is substantially amorphous andmore stringent control of fluid temperature and pressure during drawingis required in order to insure uniform levels of shrinkage andretraction. When yarn of minimum shrinkage is desired, it has been foundthat more uniform property levels are obtained when the spin-drawoperation is followed immediately by a coupled, controlled relaxationstage. The additional reductions in shrinkage and retraction are notaccompanied by an unacceptable reduction in initial modulus when theprocess of this invention is employed in the drawing stage.

After drawing with extremely hot air or superheated steam, it may bedesirable to treat the yarn with moisture, preferably prior topackaging, in order to permit the yarn to regain its normal orequilibrium moisture content. Such moisture may be supplied during asubsequent relaxation stage merely by using steam as the relaxingmedium. This combined procedure usually leads to further improvements inyarn properties.

The filamentary structures of this invention may contain the usualtextile additives such as delustrants, antioxidants and the like. Inthis respect, the presence of an antioxidant may be desirable when gasat very high temperature is employed. Suitable antioxidants aredisclosed in US. Patents Nos. 2,705,227, 2,640,004, and 2,630,421. Otheruseful additives are disclosed in US. Patents Nos. 2,510,777 and2,345,700. In addition, finish may be applied to the structures, thoughthe uniformity of finish application is not as critical as it is indrawing over or about snubbing elements.

The products of this invention are useful in all conventional textileand industrial applications, especially those which require yarn ofimproved dimensional stability. Because of their reduced retractionvalues, the drawn yarn can be packaged on inexpensive disposableshipping cores. The high modulus makes them especially suitable for usein fabrics requiring improved resilience and wrinkle resistance.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. In a high speed process, the steps of drawing nylon filamentary yarnand, in the draw zone, separating the yarn and heating the filamentssubstantially instantaneously to the draw initiation point by passingthe yarn through an enclosure and, in said enclosure, impinging a jet ofa single-phase heated gaseous fluid thereon in intersecting relationshiptherewith, the time-temperature-pressure relationship of yarn exposurebeing such as to heat the yarn to a temperature of at least C. in theenclosure.

2. The process of claim 1 wherein the fluid is superheated steam.

3. The process of claim 1 wherein the fluid is air.

4. In a high speed process, the steps of: drawing nylon filamentary yarnin a single stage and, in that stage separating the yarn and heating thefilaments substantially instantaneously to the draw initiation point bypassing the yarn through an at least partially restricted zone and, inthat zone, impinging a jet of a single-phase high temperature gaseousfluid thereon in intersecting relationship therewith, thetime-temperature-pressure relationship of yarn exposure in said zonebeing such as to reduce the drawing tension to no more than 75% of thetension on the yarn in the absence of said fluid.

5. In a high speed process, the steps of: drawing filamentary yarn spunfrom a composition consisting essentially of polyhexamethylene adipamideand, in the draw zone, separating the warn and heating the filamentssubstantially instantaneously to the draw initiation point by passingthe yarn through an at least partially restricted zone and, in thatzone, impinging a jet of a single-phase heated gaseous fluid thereon inintersecting relationship therewith, the time-temperature-pressurerelationship of yarn exposure ture of at least 115 C.

in said zone being such as to heat the yarn to a tempera- ReferencesCited UNITED STATES PATENTS Lodge 264-210 Griehl 264210 Claussen et a1264210 Oberly.

FOREIGN PATENTS 10/ 1956 Great Britain.

DONALD J. ARNOLD, Primary Examiner.

US. Cl. X.R.

